The
Sandisk Extreme 64GB is one of the fastest USB flash drives out there with a sequential read/write 197MB/188MB sec. It isn't the fastest in sequential read/write but when transferring many small files it may be the fastest USB flash drive out there.
Most flash drives when confronted with transferring many small files, as opposed to a single large file, see their transfer rates drop by huge amounts. The Sandisk Extreme apparently excels with small file transfer and can end up performing many times faster than other drives that have comparable transfer rates on large files.
The
Kingston DataTraveler Ultimate 3.0 Generation 3 (G3) 64GB 180/84MB sec. is a pretty decent drive.
A more budget oriented drive is the
Kingston DataTraveler R3.0 96/47MB sec. which come as large as 64GB.
The largest Sandisk Extreme is 64GB so if you want 128GB you will have to look elsewhere.
You might consider
Patriot Supersonic Magnum 128GB USB 3.0
($144)
Newegg
Kingston HyperX DataTraveler HyperX 3.0 128GB USB 3.0
($240)
CORSAIR Voyager GT 128GB USB 3.0
($135)
if going larger than 64GB.
Most of the larger 128GB USB 3.0 flash drives seem pretty decently fast -- at least as far as sequential read/writes go. It may come down to local availability and price if you do not buy online. Both the Kingston (Ultimate 3.0 and DT R3.0) apparently do quite well in the many small file scenario too.